This invention relates to joints between fibre-optic communications cables and in particular to methods of, and ferrules for use in, making such joints.
Fibre-optic communications cables generally include some form of strength member to carry the strains involved in installing the cables in ducts or laying them underwater, since the fibres are not capable of bearing such strains themselves. When two fibre-optic cables are jointed there must, therefore, be means provided at the joint to transfer the strain from one cable strength member to the other cable strength member.
In the case of fibre-optic cables which are used for submarine purposes, it is necessary that the cable also includes metallic conductors for use in supplying electrical power to regenerators, which must be employed when the optical fibres are used for relatively long distances. When jointing such cables means must also be provided for jointing the metallic conductors. One such form of fibre-optic cable is disclosed in U.S. Pat. No. 4,239,336 in which individually clad optical fibres are arranged in an aluminum tube which acts as protection in the form of a C-section in which the fibres are laid, the split being sealed by soldering or welding, thereby forming a pressure-resisting protective tube around the optical fibres. The tube is surrounded by a cylindrical strength member formed, for example, by one or more layers of high tensile steel wires or synthetic fibres, and this member is surrounded by a layer of copper tape, which acts as a conductor for the supply of power to the regenerator, which tape is in turn surrounded by a layer of dielectric, for example polyethylene.
One method, involving the use of ferrules, for jointing two fibre-optic communications cables is described in my co-pending U.S. patent application Ser. No. 050,377, filed June 20, 1979, now U.S. Pat. No. 4,252,405.
This method involves terminating each cable end into a respective ferrule sleeve portion, jointing the optical fibres of the cables, and securing the ferrule sleeve portions together. The joints between the optical fibres are arranged in a cavity within the ferrule sleeve portions together with a folded up length of the optical fibres.